A hydraulic circuit apparatus arranged so as to supply fluid under pressure discharged by a hydraulic pump into hydraulic cylinders for a work implement through operating valves is heretofore well known.
In case of conducting earth scraping-off operation and slope correcting operation by a power shovel, it is necessary to perform an inching operation of the work implement of the power shovel. This inching operation of the work implement is achieved by supplying extremely small amounts of fluid under pressure discharged by a hydraulic pump into hydraulic cylinders for the work implement.
In pressurized fluid supplying apparatus circuits of the prior art, in order, to control the amount of fluid under pressure to be supplied into hydraulic cylinders for the work implement, the area of opening between the pump port and the outlet port is precisely controlled by minimizing the operational stroke of operating valves. However, it is impossible to precisely control finely the amount of fluid under pressure to be supplied into the hydraulic cylinders for the work implement only by precisely controlling the area of opening. It is also impossible to inch the work implement as desired, and as a result, the operational accuracy in earth scraping-off operations and slope correcting operations is diminished.